CA2108428A1 - Detection, correction and display of digital video information - Google Patents

Detection, correction and display of digital video information

Info

Publication number
CA2108428A1
CA2108428A1 CA 2108428 CA2108428A CA2108428A1 CA 2108428 A1 CA2108428 A1 CA 2108428A1 CA 2108428 CA2108428 CA 2108428 CA 2108428 A CA2108428 A CA 2108428A CA 2108428 A1 CA2108428 A1 CA 2108428A1
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CA
Grant status
Application
Patent type
Prior art keywords
video signal
means
video
format
color
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2108428
Other languages
French (fr)
Inventor
Daniel R. Mcgee
Matthew H. Klein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HP Inc
Original Assignee
HP Inc
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Filing date
Publication date

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00Details of colour television systems
    • H04N9/64Circuits for processing colour signals
    • H04N9/641Multi-purpose receivers, e.g. for auxiliary information

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention legalizes a video signal (e.g., 4:2:2 format) being processed in one format so that the video signal can be transformed to other formats (e.g., analog composite NTSC format). An editor can be notified of color legalities in a video signal. Further, each pixel of a video signal can be corrected to the nearest legal value by applying soft limits and gain slopes to a constant luminance color correction process (218) . In accordance with the present invention, illegal colors of a video signal can be highlighted (238) to provide an output drive (244) for a video display which can be easily monitored by an editor.
Alternate features of the present invention relate to error detecting and monitoring (214) by assigning a specific, unique address to each video frame of a video signal. A further feature of the present invention relates to use of a pixel selecting means (252) which receives 4:2:2 video data in either serial or parallel form. The data is converted to an analog component format and used to drive a video display monitor where the video image is displayed.
The pixel selecting means can, for example, include a mouse/trackball input (256) which is correlated to the video display monitor.

Description

21~8428 PATENT
Attorney Docket No. 1093094-1 DETECTION, CORRECTIO~ AND D~8PLAY OF
DIGITAL VID~O INFORMATION
BACl~GROlJND OF q!llE INV~ION ;~

Flel~ of the Invontion ~
The present invention relates generally to video signal processing, and more particularly, to detection, correction and display o~ video signals.
8tat- o~ th- Art s ~ :
During video signal processing, numerous data formats are used to represent image information associated with each pixel of a video field so that an original image can be faithfully reproduced. For example, one common color ~ormat represents a color using red, green, and blue color components. With this color ~ormat, the color o~ each pixel $s represented by quantities of red (R), green (G) and blue (B) color components detected in the original image (rererred to hereafter as an R,G,B ~ormat).
Another ~ormat u~ed to represent a particular color is by the amounts o~ hue (e), saturation ~8), and luminance ~Y) included therein ~re~erred to herein 2S as the Y,S,e ~ormat).
Table 1 lists these two color ~ormats, along with three additional color formats~
_ _ ~ ~ I ::
R~ed Ylu_c Ylumin~co Y~i~ Y~co I . ~ ' 1~ 30 G~ 8--~ Cch~i_ cb~ cr~b~ ~ ~.

3 l ~ ~
~. C,ebl~, ,,,, uo Vq~ Cb_ -Table 1 3S A series o~ mathematical trans~ormations exists between these various color formats. However, .,~ .
~, .

~ 2lns42s PATENT
Attorney Docket No. 1093094-1 - -because each of these color formats is implemented differently in the real world, conflicts exist in moving between them. These conflicts derive from the fact that different color formats possess s different characteristic~, such as analog versus digital characteristics and component signal versus composite signal characteristics.
For example, the R,G,B color format is an analog forfflat because the video signal~ are analog in nature and vary, for example, between 0 and +0.7 volts. Further, the R,G,B format is a component format because the entire video signal is transmitted in 3 component parts using three `-~
separate R,G,B signal paths. A common use of this transmission format i~ in computer graphics eguipment and computer displays. This can be contrasted with a composite video signal, where the video signal is contained and transmitted in its entirety on a single signal path.
A Y,U,V format is an analog component format which is very ~imilar to the R,G,B, format. The Y,U,V format include~ a luminancs ~Y) component, an in pha~e chroma component (U) and a guadrature phase component (V). This format separates luminance (or brightness) information from chrominance (or color) information, wherein Y represents luminance, and U ~`
and V together represent chrominance. The Y,U,V
format is sometimes preferred over the R,G,B format because a black and white monitor can be driven with just the Y signal. A transformation between the R,G,B and Y,U,V format is as follows~
Y = .299 * R + .587 * G + .144 * B `~
35 U = -.148 * R - .289 * G + .437 * B O < R,G,B, < 1 V = .615 * R - .515 * G - .100 * B

' 2~8~28 PATENT
Attorn~y Docket No. 1093094-1 A ~,Cr,Cb format is a digital component format specified by the international standard set forth in ~ ~ -CCIR 601/656 and frequently referred to as the 4:2:2 format. Generally speaking, the Y,Cr,Cb components are digital versions of the Y,U,V analog components.
The "4:2:2" designation refers to the use of a sampling rate for U and V components which is one half the samplQ rate for the Y component. For example, the Y component is sampled at 13.5 Mhz and the U and V components are sampled at 6.75 Mhz each.
The precision of the digitization is typically 10 bits.
The 4:2:2 $ormat i8 considered a high quality format and is therefore preferred for U8Q in high lS end post production studios. Video signals received by a post production studio in another color format are typically transformed or converted from other color format~ to the 4:2:2 format before editing begins. For example, analog components of the Y,U,V
~ormat can be converted to components in the 4:2:2 format using the following mathematical trans~ormation:

Y~4:2:2) ~ Y *876 + 64 dec~mal Cr = ( (V/l .2296) + .5) 896 + 64 decimal ~.
Cb = ((~r/.8736) + .5J as6 + 64 decimal In contrast to component formats, a composite format encodes an entire video signal onto one signal path. An analog composite format is used primarily to distribute a video signal from an originating facility to a viewer where it is decoded and displayed on a television receiver. There are two primary analog composite formats: NTSC, used 3s mainly in North America and Japan, and PAL, versions of which are used throughout Asia and Europe. The ~ ' ` ~ 2 1 ~ 2 8 PATENT
Attorney Docket No. 1093094-1 composite NTSC format can be derived from the analog component Y,U,V format using the following mathematical transformation:

Amplitude = [(Y + CJ * .925 + .075] * .714 volts C = v * sinfwt + .576) + U * cos(wt + .576J
~ = 3 . 579545 MHz A similar derivation exists ~or transforming the composite PAL format from the analog component Y,U,V
format.
A typical use of various color formats in a post production studio is illustrated in Figure 1.
As mentioned previously, real world implementation~
impose restrictions on final values derived when trans~orming one color format into another color format. These restrictions can render a color which is legal in one color format, illegal in another color format.
As referenced herein, a "legal color" is a color which can be accurately reproduced by conv~ntional video equipment in a givon color format. An "illegal color" is a color which is outside the color space of conventional video 2S equipment and which cannot be faithfully reproduced by the video equipment.
For example, where the Y,Cr,Cb components of the 4:2:2 format are each represented with a 10 bit word, each of these words must remain between a digital value of 0 and a digital value of 1024 decimal. In a typical analog R,G,B format, the individual R,G,B component signals must remain between 0 and 700 mV. The analog composite NTSC
signal must typically remain between -142 mV and 785 3s mV (the limits for the PAL analog composite signal are slightly different). Transforming a legal 4:2:2 ;

21~8~28 PATENT
Attorney Docket No. 1093094-1 signal to one of these analog formats does not guarantee a legal analog signal. However, transformations between these various formats often can not be avoided.
For example, the output format of a post production studio must be analog composite to be compatible with typical end user (e.g., viewer) equipment. Because some po~t production studios pre~er using thQ higher quality 4:2:2 digital ~o component format for editing, transformation from the 4:2:2 format must be performed once all editing has been completed.
If an illegal analog composite signal exceeds predetermined limits (e.g., color space limits of conventional video equipment), the resultant video waveform will be distorted. For example, voltages greater than 785 mV (for NTSC) frequently stress the dynamic range of video tape recorders and clip the video signal being reproduced. Such clipping renders the resulting color of the video signal unpredictable.
o~ten the result Or distortion due to ill~gal colors can be much more seriou~, causing entire portions o~ the picture to be significantly 2S different from what was intended. For example, a pixel that i8 100% amplitude yellow corresponds to -~ -legal values of 100% Red and 100% Green in the R,G,B
component format. When this pixel is converted to the 4:2:2 format and then to the NTSC composite analog format, the peak voltage levels are 935 mV
and 343 mV. 935 mV is significantly above a legal NTSC signal amplitude of 785 mV and cannot be represented in the NTSC format. In other words, 100% yellow is a lega} R,G,B color but an illegal 3s NTSC color.

~:~08~28 PATENT
Attorney Docket No. 1093094-1 If the video image is edited in an analog composite format, the editor can simply ensure that no signals above (or below) a certain limit are created. However, because editing in a 4:2:2 post s production studio is done in a digital component format, the editor does not know what the peak analog composite levels will be after conversion.
Further, each individual pixel in the video field has a different peak level and it i~ impossiblQ for the editor to individually track every one. Thus, in a 4:2:2 post production studio, it i8 likely that colors the editor creates or acquire~ from other color formats cannot be represented in the analog composite format.
A first conventional approach used to address the foregoing problem takes the video signal in the 4:2:2 format and, at various monitoring points in the post production studio, converts it to an analog composite format. The analog composite signal can then be viewed on a traditional waveform monitor and the peak excursions measured to identi~y illegal colors.
There are at least two disadvantages to this first conventional approach. First, the waveform monitor displays all pixels of the vides display in real time as they occur. For NTSC, there are approximately 14 million pixels every second. At this rate, it is impossible for the editor viewing the video signal waveform to detect every illegal color. Secondly, this conventional approach can only notify the editor that an illegal color has been detected.
A second conventional approach is referenced in a document entitled "The Chroma Predictor", from 3S Encore Video Industries in Hollywood, California.
This document describes receiving a video signal in PATENT
Attorney Docket No. 1093094-1 the 4:2:2 format. Pixels of the video signal which are determined to be illegal are corrected to the nearest legal color of the 4:2:2 format in real time and merged with the legal 4:2:2 signal at an output.
The result is a signal in the 4:2:2 format that is guaranteed to be legal when a final transformation to an analog composite format is made.
A key feature of this second conventional approach is that chrominance i~ reduced to render an illegal color legal, whilQ hue and luminance are maintained constant. For example, once a color associated with a given pixel is determined to be illegal, the two chrominance values are ad~usted as ~ollows:
; ~
Cr' = X ~ (Cr-512) + 512 decimal Cb ' = X ~ (Cb-512) + 512 decimal where Cr', Cb' are "legalized" versions of Cr and Cb; Y remains unchanged to preserve constant luminance. Further, the ratio between Cr and Cb remains unchanged to pre~erve con~tant hue. For an NT8C compo~ite input video olgnal ~V~), X lo determined as ~ollow~:
when Vin(h~ghJ > H~LlMlT(~gh)~
X = [ (H~RDLlA~lT(high)/7.14 - 7.5J/92.5 - Pyl/C for ~SC
when ~n(low) < ~IA~WMIT(low):
X = 1(7.5 - HA~LlMlT(low)/7.14J/92.5 + Pyl/C for NTSC
wheK: Py = (Y (4.2.2:) - 64J/876 Pr = (Cr - 64J/89~0.5 Pb = (Cb - 64)/896 0.5 U=0.874~Pb V=1.23~Pr C=f~r2+VA2rO.5 HAP~LIMITS are in millivolts ~ - ~10~28 PATENT
Attorney Docket No. 1093094-1 The disadvantage of this second approach is that it does not maintain the contrast of the original image in all areas of the image. For example, if an image of the sun contained many different levels of s brightness, all of which are determined to be illegal, the entire image would be clipped to the HARDLIMIT value in the foregoing equation. This would distort the image by eliminating some or all of the original contra6t.
In addition to the distortions which result from transforming illegal colors, conventional digital video processing systems are also susceptible to other drawbacks. For example, conventional systems u6ed for processing a 4:2:2 lS digital video signal are unable to accurately detect, identify and log digital data errors - ;
relative to frames of the video signal in which they exist.
Conventional video processing systems merely tell an editor where errors occurred in a very general sense; i.e., by identifying an amount of time ~ince the la~t error wa~ doto¢ted. The~e systems do not describe exactly what video frames contain errors. Further, they do not tell the 2S editor if any other errors occurred before the last error. Thus, errors that occur over a period of ;
time are not individually noted and logged.
Another problem with video signal processing in a post production studio i8 the routing of the video signal from place to place using digital formats.
This routing of digital ~ignals hinders any useful display of the data for analytical or qualatative purposes.
Accordingly, there is a need for more effective -~
3S processing, analysis and display of digital video data. -~
"- "'~ '.

" ` 21Q~28 PATENT
Attorney Docket No. 1093094-1 Page g 8~MMARY 0~ THB INVENTION
The present invention legalizes a video signal being processed in one format (e.g., 4:2:2 format) so that the video signal can be transformed to other s formats (e.g., analog composite NTSC format). An editor can be notified of color illegalities in a video signal. Further, each pixel of a video signal can be corrected to the nearest legal value by applying soft limits and gain slopes to a color correction process, such as a constant luminance, constant hue color correction process. In accordance with the present invention, illegal colors of a video signal can be highlighted to provide an output drive for a video display which can be easily monitored by an editor.
Alternate features of the present invention relate to error detection and monitoring by logging a specific, unique addrQss of each video signal frame that contains an error. In accordance with the present invention, each detected error in digital data of a video ~ignal i~ logg-d with ~
frame identi~ier (e.g., an 8MPTE time code) that correspond~ to the frame in which the error occurred. ~his error detection capability allows an 2S editor to review all detected errors along with their corresponding frame identifier. An error logging memory which records all detected errors and associated frame identifiers can be cleared to, for example, start a recording session or permit additional logging after the memory is full.
A further feature of the present invention relates to use of a pixel selecting means which receives 4:2:2 video data in either serial or parallel form. The data i8 converted to an analog component format and used to drive a video display monitor where the video image is displayed. The ~.~0(~28 PATENT
Attorney Docket No. 1093094-1 pixel selecting means can, for example, include a mouse/trackball input which is correlated to the video display monitor. As the mouse is moved, its movement is decoded and superimposed with a cursor s on the component analog video signal. An internal display tracks movement of the mouse and displays a current line number and column number of the video display monitor (i.e., a selected pixel location) over which the cursor is presently located, as well as actual video signal data corresponding to that pixel.
In an exemplary embodiment, the present invention relates to a system which includes a system for processing a video signal comprising a ;
video signal input means for receiving a video ~ ;~
signal, controller means for receiving input ~ ~
commands and for providing control signals to said -system in response thereto, monitoring means for detecting errors in said video signal, said monitoring means storing each detected error with an associated ~rame identifier, detecting means receiving said video signal ~rom said monitoring ``
means ~or detecting and correcting illegal color information in said video signal, pixel identi~ication means for identifying video data in ``
said corrected video signal which corresponds to a predetermined pixel location of said video display, and display driving means for driving a video display in response to said corrected video signal ~
~ ~ -~RIEF D~8CRIPTION OF ~E DRA~ING8 The present invention can be further understood with reference to the following description and the appended drawings, wherein like elements are provided with the same re~erence numerals. In the drawings:
' ~' ` - 21 Q8~28 PATENT
Attorney Docket No. 1093094-1 Figure 1 illustrates exemplary video signal formats used in a 4:2:2 post production studio;
Figure 2 is a block diagram of a video signal processing system in accordance with an exemplary s embodiment of the present invention;
Figure 3 is a graph illustrating exemplary soft and hard limits which can be used in accordance with the Figure 2 embodiment;
Figure 4 is a graph illu~trating exemplary hard limits, soft limits and gain slopes to ad~ust illegal colors in the exemplary Figure 2 embodiment;
and Figure 5 illustrates a piecewise implementation of exemplary hard and soft limits in accordance with the exemplary Figure 2 embodiment.

DETAILFD DF8CRIPTION O~ T~F PREFERR~DLBMBODIMENT8 ~. Vld-o 81gn~1 I~put Figure 2 shows an exemplary system 200 for processing a video ~ignal in accordance with the present invention. The ~ystem 200 in¢lude~ a video signal input meano 202 ~or receiving a video oignAl.
The video ~ignal input mean~ hown to include a 2S parallel input 204 ~or receiving the video signal in a parallel ~ormat, and a serial input 206 for receiving the video signal in a serial format.
In the Figure 2 embodiment, the video signal is illustrated as being received in a digital component format such as the 4:2:2 video format. However, those skilled in art will recognize that the video signal can be received in any available video format and converted to the 4:2:2 video format or to any other desired video format for processing in the system 200. The exemplary Figure 2 embodiment is discussed herein as processing the video signal `` 210(~28 PATENT
Attorney Docket No. 1093094-1 using the 4:2:2 video format since this is the format nsed by typical post production studios to achieve high signal quality during editing.
The exemplary Figure 2 system is designed for parallel processing of the video signal.
Accordingly, the video signal input means includes an output 212 for producing a parallel digital output in response to a video signal received on either the parallel input 204 or the serial input 206. While a video signal received at the parallel input 204 can be directly processed by the system 200, a video signal received at the serial input 206 must be converted to a parallel format. A serial~
to-parallel converting means 208 is provided for this purpo~e.
Devices for converting a serial signal to a `;
parallel signal, such as the "Serial ~ ~ ;
Inter~ace/Transmission Decoder" , SBX1602A, available from Sony, Corp., are well known and need -~
not be described in detail. The Sony SBX1602A
device can be used to convert a ~erial data ~tream received at the serl~l input 206 lnto a parallel, ll-bit data path (i.e., 10 data blts, and one clock bit) for processing in the system 200. Reference herein to an ll-bit data path is for purposes of discussion only. Those skilled in the art will ~-appreciate that any desired data paths can be used ~ -in accordance with the present invention. ~`~
The serial and parallel inputs of the system 200 are illustrated as receiving the video signal from emitter coupled logic (ECL). Typically, ECL is used to provide high speed signal processing. Those skilled in the art will appreciate that signal processing performed by the Figure 2 system 200 can be implemented entirely with ECL components, or any other digital technology.

~- 2 ~ 08~28 PATENT
Attorney Docket No. 1093094-1 To reduce fabrication cost, a slower but more cost effective digital technology such as transistor-transistor logic (TTL) can be used to perform video signal processing in the Figure 2 S system. Accordingly, the exemplary video signal input means 202 includes converting means 210. The converting means 210 converts the video signal received at the parallel input 204 or the serial input 206 ~rom a first logic technology (e.g., ECL) to a second logic technology ~e.g., TTL). Further, the converting means can include a latch, such as a D flip-flop, for latching the converted, parallel video signal at the output 212.
In accordance with an exemplary embodiment, a lS video signal received at the parallel input 204 can be a 10 bit data stream generated at a frequency of 27 Megabyte~/second. An exemplary video signal received at the serial input 206 can be a waveform having an 800 mV peak amplitude, generated at a frequency of 270 Megabites/second. The video signal produced at the output 212 can, for example, be a 10 bit data stream generated at a rate o~ 27 Megabyte~/~econd.
In an exemplary embodiment, the video signal input means 202 amplifie~ the relatively low peak video signal received at either the parallel or the serial input. This ampli~ication permits attenuated signals to be processed in accordance with the present invention (e.g., signals which have travelled over a relatively long cable prior to receipt by the system 200).

2. ~rror Monitoring An~ Logging In an exemplary embodiment, the Figure 2 video signal processing system 200 includes a monitoring means 214 for detecting errors in the video signal.

~08~i28 PATENT
Attorney Docket No. 1093094-1 The monitoring means receives the digital video signal from the output 212 and monitors the video signal for digital data errors. In an exemplary embodiment, the monitoring means includes a conventional error detection and handling (EDH) device.
Proposed SMPTE specification RP165, set forth in a document ent$tled "Error Detection Checkwords and Status Flags ~or U88 in Bit-Serial Digital Interfaces for Television" describes a technique for error detection and handling (EDH) using checksums. ~ ~ -The goal of EDH is to provide some monitoring capability as to the quality of a 4:2:2 digital video signal as that signal is moved from place to place within a post production studio. -EDH is used to detect errors as follows. At a source of the video signal, a series Or chQcksums are computed from the video data on each frame and stored in specific places within the video signal.
At a destination of the video signal, the checksums are recomputed and compared with those stor~d at the source. If th~ checksum~ comput~d ~t th~
de~tination are di~fer~nt than tho~ comput~d ~t thQ
~ource, an error is r~gistorod and reported.
A typical use of EDH in a post production studio involves an editor taking pieces from many different sources and combining them into one tape on a de~tination tape recorder. The EDH checksum is inserted on all source equipment and monitored at the destination tape recorder. If errors are detected at the destination tape recorder, the editor re-records those frames where errors occurred.
The problem with this approach is that editors currently monitor for errors by monitoring the playback heads of a destination tape recorder on a 2108~28 PATENT
Attorney Docket No. 1093094-1 video monitor. This is particularly stressful for the editor because recording sequences are typically quite long.
A conventional error logging device is available from Textronix, Inc. for recomputing checksums and recording errors. This device permits the editor to periodically check ths error logging device to see if errors had occurred. However, frames that are determined to have error~ are not marked in any particular way. A capability i5 merely provided to notify the editor of how much time has elapsed since the last error was detected.
Thus, conventional devices only tell the editor where errors occurred in a very general sense; i.e., by identifying the time since the last error. They do not describe exactly what video frames contain errors. Because conventional devices do not tell the editor ~f any other errors occurred before the last detected error, two areas of error data on the source tape cannot be communicated to the editor.
In accordance with a ~ignificant feature of the present invention, a frame id-nti~ier i~ u~ed to uniqu~ly identiry thQ rram- in whi¢h an error wa~
detected. In an exemplary embodiment, the SMPTE
2S time code which is included in a typical video signal can be used as the frame identifier. SMPTE
time codes are well known in the television industry as a standard way of identifying specific video frames. For example, video tape recorders use the SMPTE time code to shuttle a tape to an exact video frame specified.
When the monitoring means 214 of the Figure 2 system detects errant digital data in a frame of the video signal, a flag is set in a conventional manner as described in the previously mentioned SMPTE RP165 document entitled "Error Detection Checkwords and 21 08~28 PATENT
Attorney Docket No. 1093094 Status Flags for Use in Bit-Serial Digital Interfaces for Television. n In accordance with the present invention, a flag generated in response to detection of errant digital data is stored in a s register of the monitoring means. Further, a frame identifier (e.g., SMPTE time code) associated with the frame in which errant digital data was detected is also stored in a register.
By maintaining a log of all detected errors along with an associated ~rame ldentifier, an editor can acces~ a complete listing of all errors which occur in the video signal. Using the frame identifiers, the editor can quickly move to affected areas of the video signal and re-record bad frames at any time.
Such errors and associated frame identifiers can be displayed on request to the editor. The ~ ~
frame identifiers can be used by the editor to - ~i quickly and easily correct errors in the video signal. Further, the ~rame identifier~ allow the editor to re-record the exact frames that are bad with enhanced accuracy since there is no ambiguity a~ to where the error~ exl~t ln th- vldeo ~ignal.
Error logging ln thl~ way guarantee~ all errors will be logged.
In accordance with the exemplary Figure 2 embodiment, errant digital data and associated frame identifiers detected by the monitoring means are logged by a system controller, represented as a controller means 216. Communication between the monitoring means 214 and the controller means is performed via a detecting means 218, which is used for color correction in the Figure 2 embodiment. In an alternate embodiment, communication can be 3s performed directly between the monitoring means the controller means.

; T t~

~0.~28 PATENT
Attorney Docket No. 1093094-1 3. 8y~te~ controller The controller means 216 receives editor input commands via a keyboard 270 and provides control s signals to the system in response thereto. In an exemplary embodiment, the controller means can include a Motorola 68331 microprocessor and memory (e.g., EPROM and RAM with battery back-up). Power to controller means, and to all other components of the Figure 2 system is provided by a power supply 272. Internal memory associated with the controller means 216 can serve as a logging means for storing errors and associated frame identifiers detected by the monitoring means.
As described above, the controller means 216 logs a frame identifier for each video frame of the video signal in which errant digital data is detected by the monitoring means. The controller means 216 includes a recording mQans for storing the frame identifier whenever any error in the video signal is detocted, such that the errors are logged with the ~rame identifier. In add~tion to logging all recorded error~ in the controller mean~ 216, a signal reflecting detection Or each error can be 2S output from the system 200 via a by-pass 250.
Further, each detected error can be used to activate an audible output 274.
A standard RS422 link 217 can be used to remotely control the controller means 216. By using such remote control, a plurality of the Figure 2 systems, each having a controller means (e.g., a controller means 216) can be controlled and monitored from a single remote location. For example, the total number of errors detected in one or all of the controller means can be monitored remotely.

`` 21Q~428 ~;
PATENT
Attorney Docket No. 1093094 Page 18 ~
The controller means 216 also represents a :
editor interface for controlling a detecting means ~::
218. The detecting means detects and corrects illegal colors in the video signal.
. Illegal Color Det-¢t~on Aad Correct~on The detecting means 218 receives the video ~ ` ;
signal 4rom the monitoring means 214. Alternately, where the monitoring means 214 is not included in `:~
the Figure 2 system, the detecting means can receive a video signal directly from the input means 202.
In the exemplary Figure 2 embodiment, the :.
detecting means receives the video signal in a 10~
bit, 4:2:2 video format. The detecting mQans 218 is lS provided for detec*ing and correcting illegal color information in the video signal while maintaining contrast of at least a portion of the corrected video signal proportional to contrast o~ the uncorrected video oignal. .
To correct illegal color information while still maintaining contra~t proportional to that of the uncorre¢ted video olgnal, tho detecting meano 218 o~ the Figure 2 oyotem includeo a color correcting means 220 and a storage means 222. In an : : .
2S exemplary embodiment, the color correcting means 220 of the detecting means 218 can be con~igured as a field programmable logic array (FPGA). The use of a field programmable logic array to implement the logic associated with the function of thi~ block permits relatively high speed, real-time processing to be performed on the digital video signal received from the output 212. For example, a field programmable logic array available from Xilinx Corporation can be used to perform 10 bit parallel 3s processing of the digital video signal.

08~28 PATENT
Attorney Docket No. 1093094-1 In an exemplary embodiment, the storing means is a SRAM device for storing predetermined criteria.
The SRAM device is programmable in response to control signals from the controller means 216. The s storage means 222 stores predetermined criteria represents control information which distinguishes a legal color of the video signal from an illegal color. The predetermined criteria are programmed by the editor based on a desired output format of the video signal.
For example, where a desired final format is an analog composite format, the predetermined criteria constitute 4:2:2 video signal color limits. The color limits identify colors in the 4:2:2 video signal which can not be transformed into a legal analog composite signal. Analysis of the video signal to detect illegal colors is performed on a pixel-by-pixel basis.
In accordance with a significant feature of the present invention, the color correcting means 220 identifies pixels of the video signal which contain an illegal color and ~eloctlvely leg~llzeo color~ of the video sign~l. In addition, the color correctlng means 220 produces a 3-bit mark to label pixels which contain illegal color information based on the predetermined criteria.
To maintain contrast of the uncorrected video signal, the predetermined criteria stored in the storing means is used to distinguish illegal/legal colors and to correct illegal colors using soft limits and gain slopes. The individual Y,Cr,Cb components for each pixel of the digital video signal are used to calculate a corresponding peak analog composite value for each pixel. If these calculated values are outside (i.e., above or below) those specified by the editor as "HARDLINITS" (i.e., o(g~28 PATENT
Attorney Docket No. 1093094-1 for the output format selected by the editor), a -particular pixel is considered illegal.
For example, a pixel is illegal and should be highlighted if:

rn(hzgh) > HARDLlUlT~high) OR ~n(low) < H~LlMlT(low) where: ~n(~ighJ = [ (Py ~ CJ *.925 + .0751 ~. 714 voltsflor N~C :
~n(lowJ = ~ CJ *.925 + .075~ ~.714 wlts l~n(highJ = (Py + CJ ~.7volts forP~L
rn~10w) = (Py - CJ ~. 7 volts and, Py = (Y(4:2:V - 64J/~76 Pr = (Cr- 64J/8960.5 Pb = (C~ - 64J/896 0.5 U = Q874 ~ Pb V = 1.23 ~ Pr C = ~2 + V~2] ^05 The controller means 216 is capable of storing HARDLIMITS for both NTSC and PAL simultaneously.
Figure 3 shows an exemplary control strategy for the detecting means 218 that uses HARDLIMITS as well as SOFTLIMITS and GAIN SLOPES in accordance with the present invention. A composite value for the video signal received by the detecting means is designated V~, with a compo~ite value ~or a video signal produc~d at the output of the detecting me~ns being designated V~. A relationship of V~-V~ is maintained only until the SOFTLIMIT is reached.
i3eyond the soft limit, the relationship between V, and V~ depends on the value of the GAINSLOPE.
As shown in Figure 4, if the Gain Slope = 1 the relationship, V~=V~, is maintained until Vins>
HARDLIMIT. Beyond the HARDLIMIT, V~ is maintained at the HARDLIMIT. If, however, the GAINSLOPE is made to be less than 1, a transition from the 3s SOFTLIMIT to the HARDLIMIT is smoothed out. Smaller values of the GAINSLOPE will make the transition of V~ from the SOFTLIMIT to the HARDLIMIT slower. ;

PATENT
Attorney Docket No. 1093094-1 Having a GAINSLOPE of less than 1 effectively compresses higher voltages of the composite video signal. Maintaining contrast in the corrected video signal "proportional" to that of the uncorrected video signal refers to an ability of the detecting means to preserve the original image contrast when legalizing a video signal. In this sense, the term "proportional" represents compression of at least a portion of the original video signal to establish at least one SOFTLIMIT whereby the GAINSLOPE i~ r~duced below 1Ø Thus, GAINSLOPE values can be selected to reduce or eliminate the number of illegal colors of the uncorrected video signal which are clipped at the HARDLIMIT.
In accordance with exemplary embodiments, a relationship between V, and V~ i8 implemented in a piecewise linear rashion. For example, Figure 5 shows various linear regions of Vin that are used in an exemplary embodiment. A value of X is determined such that:

Cr' = X~(Cr - 512) + 512 decimal Cb' - X~(Cb SIV + 512 dec~mal where Cr' and Cb' are ad~u~ted value~ Or Cr' and Cb'.
The value~ of B1 through B6 are arrived at using the following equations:

uRDLDa7~ so~ SO~
2~SLOrE(lDW) ~108~2~ ~

.
PATENT ~, ;
Attorney Docket No. 1093094 B3-SOl;~lo~
~4-SOFTl~hl8h) . . - ~. , BS. [~WL~ (high)-So~;~htgh)] +so~;~hi8h) 2~SLOPE(hl8h) . .
B6~ ~) +so~Tl~JrIr~ht8h) ~ .

.':'~ '-.',.;.

These equation~ for Bl through B6 describe 7 regions and 7 values of X. The value of X is ba~ed on the region in which Vin is located. The regions are as described below:

Region 1: Vin~B1 . ~-Region 2: B1~-Vin~B2 Region 3: B2~-VincB3 Region 4: B3~-Vin~B4 Region 5: B4~-Vln~B5 lS Region 6: B5~-Vin~B6 `
Region 7: B6~-Vin ,~

The values of Xl through X7 are determined as follows for NTSC, wherein hard and soft limits are in millivolts. -~ARO(low) = HARDUMlT(lowJ HARD(~ugh) = ~II~DUMIr0dgh)' ~ , . '' SOFT/low) = S SO~iT(7dgh) = SOFrU 110igh) ~' ' ` ` -, S(lowJ = G~lNSLOPE(l~v) S(~ughJ~= G~lNSLOPl~(h'gh) `: 25 '~
,, ' ' .. ::. :

- ~ 1 0~28 PATENT
Attorney Docket No. 1093094-1 Xl 5 1 7~-0.14~krw) X2N~C5 1 75~14 17~DW) S(~ 2.51S~ow) 7.5~0.14 SO~-S~low-0.14 H,~lRD(~ow) 92.5~-~gS

X3N~ ~t92~ 7~-0.14SOI;~lDw IC~/0.14~SOPl~tow)]

X~

XS~ 1 [~g2 h~ 5-)~y~7~5-0~14gOl7~thl8h ~C~0.14-SOli~hl8h)~

X6~. 1 0.14~htgh)-7.5 p~, S(hi8h) ~(PYI C)92.5~S(hi8h)-7.5~0.14-gOl7~h4A) (l -S(hi8h-0.14 ll,~RD(h~h) ,, X7N~ 1 Q14-~hf8h)-7.5 ~;
Xl~ _0143~lDW),~]

8~28 : ~ :

PATENT -~ -Attorney Docket No. 1093034~

x2,~=1[~_0.143HLZ~w)_ S(~w)~-~100+0.143SOF~w)~l-S(~w-0.143h~RD(kw)l -100~2~ -X3~AL=1 [PY- (Py-C) /0-143-sO~;ltlow)-o-l43-slooF~ow)-l- S~

X4,A,,=1 ~ ~ ;

X5"",~ 1 [. 100~+C)-~S~Q143 SO~;7t.hl8h) (1-~/S(h~8h -P~,¦

X6 ,~_.143~L~xh~gh)_py+ S(hl8h)~ 1 ~-100+0.143-SOF~h~h)~1-S~h~h~.143HL~Xhigh)]
C 100 100 ~ 3~ '`

X7~ o.l43HL~xhi8h)-p~

The detecting means further includes a video data encoding means 224 for encoding the corrected video signal with error detection information. The video data encoding means 224 receives the corrected S video signal ~rom the color correcting means 220.
The video data encoding means then re¢alculates new error handling data. For example, n~w error handling data can be computed a~ ¢hecksums in accordance with the SMPTE RP165 document and encoded on the corrected video signal. The encoded information can then be used by systems receiving the corrected video signal to verify correctness of -~
the video data. This corrected video signal with the new error handling data encoded thereon can be directed to an output interface of the system 200.

5. Output Interf~ce The output interface is represented in the Figure 2 system as an output means 226 which is provided for outputting the corrected video signal -8~28 PATENT
Attorney Docket No. 1093094-1 from the detecting means in a parallel or serial format. The output means 226 includes an input 228 for receiving the corrected video signal from the detecting means 218 in a digital parallel format.
s The output means 226 further includes a parallel output 230 for directing the corrected video signal from the detecting means 218 to output terminals of the system 200. The output means 226 further includes a sQrial output 232.
The ~erial output i~ produced by a converting means 234 which converts a parallel output of the detecting means to a serial ~ignal via a parallel-to-serial converter. The parallel-to-serial converter can, for example, be configured as the lS "Serial Interface/Transmission Encoder", SBX1601A, available from Sony, Corp. The Sony SBX1601A device can be used to convert a parallel data stream received at the input 228 into a ser~al data path for output from the ~y~tem 200. The Figure 1 video signal processing ~y~tem 200 can also include a bi-pass loop for routing serial digital video data directly from the input means 202 to the output mean~ 226.
Further, the output mean~ 226 in¢lude~ a logic 2~ converting mQan~ 236 for converting the video signal routed to the parallel output 230 or to the serial output 232 from one digital logic technology (e.g., the TTL Technology of Figure 2) to another logic technology (e.g., ECL). As with the converting means 210 of the input means, the converting means 236 illustrated in the Figure 2 system represents an exemplary conversion from TTL to ECL. However, those skilled in the art will appreciate that any digital logic technologies can be used for the 3S Figure 2 system, and any ~uch digital logic technology used can be converted to any other 8 ~8 PATENT
Attorney Docket No. 1093094-1 digital logic technology for output from the Figure 2 system. Further, the output means 226 can include any necessary amplifiers for driving the video signal outputs to appropriate amplitudes for s transmission over any cable lengths connected to the Figure 2 system.
While the corrected video signal produced by the detecting means can be directly output ~rom the Figure 2 system via the output means 226, exemplary embodiments of the present invention further include a capability to highlight illegal pixels of the video signal for di~play to the editor. In an exemplary embodiment, legal pixels which are `~
adjusted to maintain contrast are not highlighted.
6. ~ighl~ghting Ill-gal Color~
In alternate embodiment of the present invention, a highlighting means 238 can receive an output of the detecting means to highlight pixels of the video signal which were identiried and labelled by the detecting m-an~ to contain ill-gal color information. The editor can select betw en various highlighting styles. For example, a pixel that has a peak value above the HARDLIMIT (high) can be made 2S bright red and a pixel that has a peak value below a HARDLINIT (low) can be made bright green.
Alternately, all legal values between the HARDLIMIT
(high) and HARDLIMIT (low) can have their luminance content reduced by a factor of two to effectively highlight those pixels that are illegal. Of course, many other highlighting techniques or selections can be used.
In an exemplary embodiment, the highlighting means 238 includes converting meanQ 240 for 3S converting the video signal from the detecting means to an analog video format. Those skilled in the art -` ` 2 ~ 2 8 PATENT
Attorney Docket No. 1093094-1 will appreciate that the converting means can be eliminated if the video signal is highlighted in the video format that this signal is received from the detecting means (e.g., a digital video format). In the exemplary Figure 2 system, the converting means 240 converts the 4:2:2 digital video signal to a desired display format, such as an R,G,B component format or a Y,Pr,Pb component format. The converting means 240 can be a conventional field programmable logic array such as an FPGA available from Xilinx Corporation.
The converted video signal produced by the converting means 240 is input to a pixel marking means 242 for marking pixels of the video signal identified as having an illegal color. Marked pixels are then merged with the analog component ;~
video signal received from the converting means 240.
The pixel marking means can, in an exemplary embodiment, be configured using a field programmable logic array such as the Xilinx device described with respect to the color correcting means.
To highlight illegal colors in accordance with the exemplary Flgure 2 ~y~tem, th- pix~l marking mean~ 242 receives the three bit lnput ~rom the 2~ detecting me~n~ which identifies, on a pixel-by-pixel basis, each pixel that was detected as having an illegal color. The pixel marking means 242 highlights each pixel of the output signal from the converting means when the mark input from the 0 detecting means indicates that a particular pixel was corrected by the detecting means 218. The exact manner by which a pixel is highlighted can be selected by the editor via a user inter~ace of the controller means 216. For example, if the editor wishes to render all corrected pixels green, then each pixel output from the converting means 240 `` 21~28 PATENT
Attorney Docket No. 1093094-1 which is associated with a mark from the detecting means would be converted to a green color. As a result, the output from the pixel marking means 242 would be the reproduced video signal wherein all s pixels would contain their corrected color unle~s an original color of that pixel location was determined to be illegal. In the latter case, all pixel locations determined to contain an illegal color by the detecting means would appear green.
The highlighting feature o~ the highlighting mean~ 238 can be selectively controlled by the controller means 216 so that it can be turned on or turned off. Where the highlighting i8 turned on, an output would be produced from the highlighting means lS 238 as discu~sed above. Where the highlighting feature is turned off, the output from the highlighting means would simply be the video signal ;~
with all pixel locations containing their corrected color a~ determined by the detecting mean~ 218. No highlighting would be included in a video signal produced from the highlighting means in this latter ca~e.
The corrected video ~ignal wlth or without the highlighting ~eature activated, produce~ an output 2S which can be u~ed to drive a video display monitor via a display driver.

7. D~pl~y Dr~v r The Figure 1 video signal proce~sing system 200 further includes a di~play driving means 244 for driving a video display in response to the corrected video signal. The display driving means include~ a first output mean~ 246 for outputting the corrected video signal from the detecting means 218 in an analog composite format, such as the NTSC format or the PAL format. The flrst output means 246 can be ``" ~1~8~8 PATENT
Attorney Docket No. 1093094-1 any conventional device for converting a digital 4-2:2 format video signal to an analog co~posite signal. `~-The display driving means 244 further includes s a second output means 248 for outputting the corrected video signal from the detecting means in a component format. The second output means 248 receives the corrected video signal from the highlighting means, and depending on the editor's sèlection via th~ control}er means 216, thi~ video signal can selectively include the highlighting information described previously. The second output means includes a triple digital-to-analog converter `~
for driving a video display monitor. For example, -lS the output from the triple digital-to-analog converter can be used to directly drive an analog compor.ent monitor.
Th~ ability of the display driving means to provide both component and composite outputs from the system 200 provides the editor enhanced ~lexibility in nitoring a video signal received by the system 200. For example, the compo~ite video signal produced rrOm the rlr~t output means 246 can be used to drive a composite monitor and/or can be 2S used to drive an oscilloscope for monitoring characteristics of the analog composite waveform.
The component output can be used to drive a video display monitor for examining those pixels which were highlighted by the highlighting means 238 and/or can be used to drive a component monitor.
While the Figure 2 system does not include a video display monitor on a front panel of the system itself, those skilled in the art will appreciate that such a video display monitor could be incorporated in the system illustrated. Further, those skilled in the art will appreciate that the `- ~.t~8~28 PATENT
Attorney Docket No. 1093094-1 display driving means can include any means necessary for implementing a desired output format of the corrected video signal.
$hus, the Figure 1 video signal processing system 200 can drive a video display monitor to highlight illegal colors, allowing the editor to easily see where problems in a video picture are located. The editor can much more easily correct illegal color problems at a location in a video image where the problems actually exist. Further, the use of soft limits and gain slopes in accordance with the Figure 1 video signal processing system permits the editor added control over how illegal ~`
colors are to be modified in a final image. By ~5 reducing the gain slope to a value of less than 1, ~ ~-the contrast of an image which includes illegal colors can be maintained, thus improving reproduction of an original image.

8. P1~ tificat~on In accordance with yet another a~pect of the present invQntion~ the Figur~ 1 video ~ignal proces~ing sy~tem 200 can be configured to furthQr include a pixel identification means 252. The pixel 2S identification means enables thQ editor to quickly, easily and accurately analyze digital video signals.
Unlike analog video signals, digital video signals can not simply be analyzed by looking at a raw digital waveform. Analyzing analog video signal information is simply a matter of connecting an oscilloscope to the video cable(s) and measuring the ;~
analog waveforms. Noise, distortions and other problems in the video information can easily be detected.
3S However, with the digital 4:2:2 video format of the Figure 2 system, the video signal is routed from 21~28 PATENT
Attorney Docket No. 1093094-1 Page 31 ;
place to place as digital data. The data is either -serialized and transmitted on a coaxial cable or transmitted in a 10 bit parallel form. Because the video information is digitized, viewing the signal s on an oscilloscope does not provide easy insight as to what information is present. Even though the oscilloscope is capable of making the same distortion measurements on the digital data as it i8 ` ::
on analog data, the end results of these measurements are much less clear when digital data is analyzed.
A significant factor which renders displaying meaningful information of a digital video 6ignal di~ficult is that the digital data is processed by lS sophisticated equalizers at the receiver. These equalizers are designed to counteract the same effects the oscilloscope might measure. Because of this, inferring actual end performance from measurements made on the transmitting cable is difficult at best.
With a digital video ~ignal, the video information is quantized lnto p~xel~ which constitutQ di~crete in~ormation packets. In the exemplary Figure 2 system, each pixel is represented 2S by three 10 bit data words. Accordingly, a meaningful analy~is of individual pixels of the digital video signal, at both source and destination locations, can provide insight into difficulties editors may be experiencing which could not bs detected from an analog signal.
Although logic analyzers have been used for ; some time to analyze digital data, they are not appropriate in this situation. Simply looking at digital data of a digital video signal on a logic 3S analyzer does not present the video information in a very useful form. For example, it is difficult to PATENT
Attorney Docket No. 1093094-~

tell exactly which portion of the original image is being observed. Also, the logic analyzer only presents the data in the form of one and zeros. -Translating this into more useful information cannot s be done without significant effort.
The pixel identification means 252 can identify video data in the corrected video signal which -corresponds to a predetermined pixel location on a video display monitor. The pixel identification means 252 includes a pixel sQlecting means 254 controlled by the editor ~or selecting a predetermined pixel location of the video display monitor. The pixel selecting means 254 includes an instrument 256, such as a mouse or trackball, which lS is selectively movable by the editor over a grid.
The grid has locations which are correlated to pixel locations on the v$deo display monitor. The pixel identification means further includes a decoding means 258 responsive to movement of the instrument 2S6 ~or correlating movement of the instrument 256 to a pixel location of the video display monitor.
Decoded output~ from the instrument 256 are lnput to the controll-r meano 216. Th- controller mean~ 216 can u~e the decoded movements o~ the lnstrument 256 to control a graphlcs controller 260.
The pixel marking means 242 o~ the highlighting means 238 can be used to superimpose an identifier generated by the graphics controller 260. For example, a cursor can be superimposed on the corrected video signal produced by the correcting means 220. Thus, as the editor selectively moves the instrument 256 on the grid, a cursor will appear to simultaneously move in a corresponding fashion ~-over the video display monitor driven by the display 3s driving means 244. m is allows the editor to 2~08~28 PATENT
Attorney Docket No. 1093094-l quickly select a particular pixel location being displayed on the video display monitor.
The video data associated with a selected pixel ~-can subsequently be displayed to the editor. For thi~ purpose, the pixel identification means 252 includes a display means 262 for displaying the video data which corresponds to the predetermined pixel location selected by the user via the instrument 256. Thus, when the editor moves the cursor to a given pixel location Or the video display monitor via movement o~ the instrument 256, the video data associated with that particular pixel location will be output to the editor via the display means 262. The display means 262 can lS include, for example, a 2 line, 40 character vacuum florescent display for printing out the pixel data.
This pixel data is accessed from the video signal included in the highlighting means, and passed via ~;-the controller meane 216 through a bufrer of the decoding means 258 to the display means 262.
The editor can selQct to have the data aesociated with a selected pixel in any number of rormats. For example, the Figure 2 eystem permits the editor to eelect on~ Or the rollowing ~lve 2~ ~orm~ts:
(A ) YCrCb ~10 bit)~ The data is converted to its decimal representation and displayed in three data fields: Y,Cr,Cb.
(b) YCrCb (8 bit) - the two least significant bits of the data are first removed; the data is then converted to its decimal representation and displayed in three data fields: Y,Cr,Cb.
(c) R,G,B - The data is converted using the following equations and displayed in three data fields: R,G,B.
R = Py -1.14 * V

,.. .

PATENT ^
Attorney Docket No. 1093094-1 B = Py - .5U * V- .394 * U
B = Py + 2.028 * U
'~
where, Py = (Y(4:2:2) - 64)/876 Pr = (C4- 64)/896- 0.5 Pb = fiCb = 64)i896- O.S
U = 0.874 ~ Pb V = 1.23 * Pr C = f U 2 + V 2 1 0. S
~d) Composite Max/Min for NTSC and Composite Max/Min for PAL - The data i5 converted u~ing the following equations and displayed in two data ~-~
fields: Compo~ite Max, and Composite Min.
Max = [ (Py + C) ~ .925 + .0751 * . 714 w~s for NTSC ~ -Min = [ (Py - C) * .925 + .0751 ~ . 714 volts Max = (Py + CJ * . 7 volts for P~
lS Min = (Py - C) * .7wlts where, Py=(Y(4.2:V-64)/876 Pr=(Cr-64)/896-0.5 Pb = (Cb - 64)/896- 0.5 U = 0. 8 74 Pb V = 1. 23 Pr C = [ U 2 + V 2 1 0. 5 ~ ~ ;
(e) Vector format:
Chroma~lmplitude - C* .7volts Chroma Phase ~ tan ~ (V/UJ
where, Py = (Y (4.2:2) - 64J/876 Pr = (Cr - ~4)/896 - 0.5 Pb = (C~ - 64)/896- 0.5 U = a874 Pb V = 1.23 Pr C = [ U 2 + V 2 ] 0.5 The pixel identification means is capable of decoding either PAL or NTSC signals.
By displaying the actual video image on a video display monitor;and using an instrument such as a ~-mousejtrackball to address any particular pixel, the ~ ;~
editor can see exactly what information is contained in the digital data stream. The information is converted and presented to the editor in the separatQ display means 262 using a format with which .:

- 21 ~28 PATENT
Attorney Docket No. 1093094-1 the editor is familiar. This provides the editor better insight as to what is being transmitted.
The Y,Cr,Cb formats allow the editor to look at the data as it is encoded onto the video data stream. Certain aspects of the system performance can thus be examined. For example, Y values in the active video image that are larger than 254 decimal (8 bit) are reserved for synchronization and should not appear in the active video region. These values can thus be identified and corrected by the editor.
Further, the R,G,B and Vector formats which are familiar to most editors can be used to color match particular areas of the video signal on the video display monitor.
The Composite Max/Min format can be used to determine if a particular pixel' 8 amplitude will be too large or too small when the video image is converted from the 4:2:2 format to the composite analog format. Amplitudes that are too large or too small lead to illegal colors and picture distortions.
It will be appreci~ted by tho~e ~killed in the art that the pre~ent invention c~n be embodied in other 8pecific ~orm~ without departing from the ~pirit or es~ential characteristics thereof. The presently disclo~ed embodiments are therefore considered in all respects to be illustrative and not restricted. The ~cope of the invention i5 indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
, ~ ' .:,'

Claims (10)

1. System (200) for processing a video signal (204, 206) comprising:
a video signal input means (202) for receiving a video signal;
controller means (216) for receiving input commands and for providing control signals to said system in response thereto;
monitoring means (2141 for detecting errors in said video signal, said monitoring means storing each detected error with an associated frame identifier;
detecting means (218), receiving said video signal from said monitoring means, for detecting and correcting illegal color information in said video signal;
pixel identification means (252) for identifying video data in said corrected video signal which corresponds to a predetermined pixel location of said video display; and display driving means (244) for driving a video display in response to said corrected video signal.
2. System according to claim 1, wherein said video signal input means (202) further includes:
a serial input (206) for receiving said video signal in a serial format;
a parallel input (204) for receiving said video signal in a parallel format;
an output (212) for producing said video signal as a parallel output in response to said video signal received on either said serial input or said parallel input; and means for converting (210) said video signal received at said parallel input or said serial input from a first digital logic technology to a second digital logic technology.
3. System according to claim 1, wherein said controller means further includes:
means for logging detected errors and associated frame identifiers (216) from said monitoring means (214) such that said errors are recorded with a frame identifier and accessible by an editor.
4. System according to claim 1, wherein said detecting means (218) further includes:
storage means (222) for storing predetermined control information which distinguishes a legal color of said video signal from an illegal color based on predetermined criteria;
color correcting means (220) for identifying pixels of said video signal which contain an illegal color in response to said predetermined criteria and for selectively legalizing colors or said video signal while maintaining contrast of at least a portion of the corrected video signal proportional to contrast of the uncorrected video signal.
5. System according to claim 1, further including:
highlighting means (238) for highlighting pixels wherein an illegal color was detected, said highlighting means further including:
means for marking pixels (242) of said video signal identified as having an illegal color.
6. System according to claim 1, wherein said display driving means (244) further includes:
output means (248) for outputting said corrected video signal by selectively highlighting pixels wherein an illegal color was identified.
7. System according to claim 1, wherein said pixel identification means (252) further includes:
pixel selecting means (256) for selecting said predetermined pixel location of said video display, display means (262) for displaying said video data which corresponds to said predetermined pixel location; and decoding means (258) responsive to movement of said pixel selecting means (256) for correlating movement of said pixel selecting means to a pixel location of a video display.
8. Apparatus for processing a video signal comprising:
a video signal input means for receiving a video signal;
controller means for receiving input commands and for providing control signals in response thereto; and monitoring means for detecting errors in said video signal, said monitoring means storing each detected error with an associated frame identifier.
9. Apparatus for processing a video signal comprising:
a video signal input means for receiving a video signal;

controller means for receiving input commands and for providing control signals in response thereto; and detecting means, receiving said video signal from said video signal input means, for detecting and correcting illegal color information in said video signal while maintaining contrast of at least a portion of the corrected video signal proportional to contrast of the uncorrected video signal.
10. Apparatus for processing a video signal comprising:
a video signal input means for receiving a video signal;
controller means for receiving input commands and for providing control signals in response thereto;
pixel selecting means for selecting a predetermined pixel location of a video display; and display means for displaying video data which corresponds to said predetermined pixel location.
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